We examined whether oligodendrocytes, neurons, and astroglia derived from the human central nervous system differ in susceptibility to injury mediated by tumor necrosis factor (TNF)-alpha and by activated CD4+ T cells acting via a TNF-independent mechanism. Injury was assessed either as cell membrane-directed (lysis), measured by 51chromium (Cr) or lactate dehydrogenase (LDH) release, or nucleus-directed (apoptosis), measured by morphologic features based on propidium iodide (PI) staining and by DNA fragmentation measured by a terminal transferase (TdT)-mediated dUTP biotin nick end labeling technique (TUNEL). TNF did not induce 51Cr or LDH release in any cell targets, but did induce nuclear (66 +/- 2% of cells) and DNA (68 +/- 2% of cells) fragmentation selectively in the oligodendrocytes over 96 hr. At this time, there was no significant loss of oligodendrocyte cell number. Nuclear injury could be induced in neurons by serum deprivation and in malignant astrocytes by the combination of TNF and low serum. CD4+ T cells activated with phytohemagglutin (pha) or anti-CD3 plus interleukin-2 induced significant 51Cr and LDH release in all target cells tested; only pha-activated CD4+ T-cell cocultures showed reduced target cell numbers. Significant nuclear fragmentation was observed only for glioma cells (22 +/- 1% of cells). Differences in susceptibility to different immune effector mechanisms and in the nature of the injury response to the same effector mediator among human CNS-derived neural cells will need to be considered in design of therapeutic strategies aimed at protecting or limiting target cell injury consequent to disease or trauma.

Oligodendrocytes (OLs) and their myelin membranes are the apparent injury targets in the putative human autoimmune disease multiple sclerosis. The basis for this selective injury remains to be defined. OLs in vitro have been shown to be susceptible to both tumor necrosis factor (TNF) and non‐TNF‐dependent immune effector mechanisms. The former involves initial nuclear injury (apoptosis); the latter, when mediated by activated T cells, involves initial cell membrane injury (lysis). In the current study, we determined whether human adult CNS‐derived OLs could be protected from the above immune effector mechanisms by selected neurotrophic factors (CNTF, BDNF, NGF, NT‐3, and NT‐4/5) or cytokines demonstrated to protect from human or experimental autoimmune demyelinating diseases (β‐interferon [IFN], IL‐10, and TGF‐β). Nuclear injury was assessed in terms of DNA fragmentation using a DNA nick‐end‐labelling technique; cell membrane injury was assessed by lactate dehydrogenase or chromium 51 release. MTT and cell counting assays were used to assess cell viability and cell loss, respectively. Amongst the neurotrophic factors and cytokines tested, only CNTF significantly protected the OLs from TNF‐mediated injury. CNTF also protected the OLs from serum deprivation‐induced apoptosis. CNTF, however, did not protect the OLs from injury induced by activated CD4+ T cells. CNTF also did not protect human fetal cortical neurons from serum deprivation or TNF‐induced DNA fragmentation, nor did it protect the U251 human glioma cell line from DNA fragmentation induced by a combination of TNF and reduced serum concentration in the culture media. Our results indicate that potential protective effects of neurotrophic factors or cytokines on neural cell populations can be selective both for cell type involved and mechanism of immune‐mediated injury. CNTF is the protective factor selective for nuclear‐directed injury of OLs. © 1996 Wiley‐Liss, Inc.

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